Automatically activated when user works with Jest tests, mentions Jest configuration, asks about Jest matchers/mocks, or has files matching *.test.js, *.test.ts, jest.config.*. Provides Jest-specific expertise for testing React, Node.js, and JavaScript applications. Also applies to Vitest due to API compatibility. Does NOT handle general quality analysis - use analyzing-test-quality for that.
SkillScore96Maintained
Automatic
◆QA & Test Engineering pack
Last verified 9/3/2026
What it changes
Passed 23 of 24 test cases with the skill, and 22 of 24 without it.
Without skill92%
With skill96%
Checks it passed that the model alone missed
Returns HttpResponse.json with HTTP status 500 from the overridden handler
1 fixed22 passed either way1 still failing0 broke
Pass-rate lift
+4 pp
Tokens
+232%
Agent turns
0%
Response time
-11%
Model gemini-3.6-flashMeasured 9/3/2026v123 of 24 cases passed with skill
Tokens, turns and time describe resource use, not a dollar price.
See it in action
A test case the skill fixed. Same model, same prompt, with and without the skill.
Prompt
I want to write a unit test for `UserList` component verifying that an error banner 'Failed to load users' is rendered when `/api/users` returns a 500 status code. Using MSW v2 in a single test, how do I override the default handler?
What was checked, without and with the skill
Checked
Without skill
With skill
Calls server.use inside the test to override default handlers
Passed
Passed
Returns HttpResponse.json with HTTP status 500 from the overridden handler
Missed
Passed
case-18 · gemini-3.6-flash · 9/3/2026 · answers are capped and redacted
What's inside
The instructions your model reads when the skill loads.
SKILL.md658 lines4 filesincludes scripts
Jest Testing Expertise
You are an expert in Jest testing framework with deep knowledge of its configuration, matchers, mocks, and best practices for testing JavaScript and TypeScript applications.
Your Capabilities
Jest Configuration: Setup, configuration files, environments, and presets
Matchers & Assertions: Built-in and custom matchers, asymmetric matchers
Mocking: Mock functions, modules, timers, and external dependencies
Snapshot Testing: Inline and external snapshots, snapshot updates
Code Coverage: Coverage configuration, thresholds, and reports
Test Organization: Describe blocks, hooks, test filtering
React Testing: Testing React components with Jest DOM and RTL
When to Use This Skill
Claude should automatically invoke this skill when:
The user mentions Jest, jest.config, or Jest-specific features
Files matching *.test.js, *.test.ts, *.test.jsx, *.test.tsx are encountered
The user asks about mocking, snapshots, or Jest matchers
The conversation involves testing React, Node.js, or JavaScript apps
Jest configuration or setup is discussed
How to Use This Skill
Accessing Resources
Use {baseDir} to reference files in this skill directory:
Create new jutsu/skills for SHINOBI WAY game. Use when user wants to add abilities, techniques, jutsu, or combat skills. Guides through all parameters and generates TypeScript code.